Stabilized zinc dust lubricant



Patented Aug. 13, 1940 UNITED STATES PATENT OFFICE STABILIZED ZINC DUSTLUBRICANT No Drawing. Application August 8, 1939, Serial No. 288,995

1 Claim.

In the drilling of deep wells such as oil wells it is common practice touse as a lubricant for the threads of casing and drill pipe a cup greasecontaining a material proportion of zinc dust.

5 These threads are repeatedly made up and broken and are set upmechanically with great force. Under such severe usage there is muchlikelihood of the threads galling, which is prevented by the addition ofthe zinc, the relatively soft metal 10 swaging down to a thin film whichprevents leakage while avoiding contact of steel with steel.

The drawback to these zinc dust greases is their impermanence. For somereason not clearly understood they generate and liberate hydrogen 15 inconsiderable quantity. For that reason they cannot be stored ordistributed in sealed packages, and open containers froth over in ashort time. t

I have discovered that by the addition to the 20 grease of a smallproportion of a fatty acid such as oleic or stearic, or of a solid fatsuch as tallow, the evolution of hydrogen is positively prevented andthe grease may be stored indefinitely. An addition of the fattysubstance in a proportion equal to of 1% of the weight of the finishedgrease is ordinarily sufflcient for this purpose, if the grease beoriginally neutral, or this quantity in addition to the quantity re- 5quired to combine with any excess alkali which may be present. Thisaddition makes no appreciable change in the lubricating or otherproperties of the grease. The fatty substance, be it a fat or a fattyacid, must be in the free form, not 10 combined with alkali as a soap.

I claim as my invention:

A thread lubricant consisting substantially of a cup grease and zincdust, rendered chemically stable by the addition of a free fattysubstance 15 selected from the group consisting of oleic acid, stearicacid, and tallow in amount sufficient to neutralize the 'free alkalineingredients of said cup grease and to leave an excess of at least 1 5 of1% by weight as referred to the finished 20 compound.

' BERT FOLDA, JR.

